Impact of Climatic Forces on the Thawing Process of a Retrogressive Thaw Slump and its Sediment and Carbon Release on the Yukon Coast, Canada

The Canadian Yukon Coast is an ice-rich permafrost coast. This is a fragile ecosystem and reacts strongly to changing environmental conditions. Retrogressive Thaw Slumps are thermal erosion features and are commonly found along this coast. They release large quantities of sediment and organic material to the nearshore zone. Arctic temperatures are projected to increase over the next century. As a result these Retrogressive Thaw Slumps are predicted to become more active and therefore release greater quantities of sediment, organic carbon and nutrients. However, a thorough understanding is lacking of the climatic forces of the erosion process of Retrogressive Thaw Slumps. In the summers of 2012 and 2013 research was conducted in a Retrogressive Thaw Slump on Herschel Island off the Yukon Coast in North-West Canada. The thawing ice-rich headwall measures over 30 m in height and 440 m in width, and undergoes erosion at a rate exceeding 9 m/yr. Two weather stations were erected, one within the close vicinity of the thawing headwall and one above the Retrogressive Thaw Slump, on the undisturbed tundra. These were measuring incoming solar radiation, temperature, precipitation and wind speed determining the microclimatic effects on the thawing of the headwall. A cut-throat flume was installed in the outflow of the Retrogressive Thaw Slump, measuring the meltwater-sediment discharge. Meltwater-sediment samples were collected in the outflow on an hourly basis and tested for pH, conductivity, sediment and organic carbon content. Data of the cut throat flume and weather stations were analysed. They show that discharge from the Retrogressive Thaw Slump is characterized by a strong intra-seasonal, as well as inter- and intra-diurnal variability. This correlates with changing microclimatic conditions, specifically temperature and precipitatio